This invention relates to increasing the reliability of joints in fluid transfer devices, and in particular to flare nut unions in refrigeration systems.
Most present day refrigeration systems utilize fluorocarbon refrigerants (FREON) being pumped through copper tubing. Gaseous refrigerant is first condensed into a liquid in a condenser, then pumped through a thermostatic expansion valve and into an evaporator portion of the refrigeration system, the now vaporized liquid refrigerant now being pumped back through a compressor and into the condenser for liquefaction, and so on, on a continuous basis. The process is repeated many times a day, continuously over a period of months and years.
A ubiquitous problem with these refrigeration systems is that they tend to leak refrigerant at the joints within the system. Unions or joints which connect the refrigerant tubing to various components of the system are generally of two types: (1) soldered (welded) union; (2) flare nut union. While a properly installed soldered joint can have good reliability over a period of time, flare nut unions are often preferred. In the case of the flare nut union installation and repairs can be effected in a simplified manner in comparison to soldering, without high temperature melting of solders, which makes flare nut unions a popular option for many refrigeration installations and repair procedures.
As was mentioned above, the problem with any type of joint is the tendency to leak, especially over a period of time. The very nature of refrigeration systems favors the development of leaks. Refrigeration compressors tend to generate substantial vibration. In the case of thermostatic expansion valves the constant high pressures, high temperature to low temperature cycling of refrigerant favors loosening of a flare nut at this junction. In addition, refrigeration systems in automobiles and trucks subject refrigerant joints to obvious additional environmental causes for refrigerant leaks. While in the past there was some degree of tolerance to fluorocarbon refrigeration leakage, today with the high cost of these refrigerants and public concern over the ozone depletion of the earth's atmosphere, preventing refrigerant leakage has become a necessity.
In this regard it would obviously be desirable to have a highly reliable refrigerant tubing connection. Attempts have been made to devise reliable high pressure fluid joints as is evidenced by U.S. Pat. No. 4,645,242. In this Positive Lock High Pressure Mounting a bell-flared collar and compression nut assembly securing a fluid flow measuring device within a pipe is disclosed. In the event of high pressure disengagement of the collar and compression nut significant disengagement of the assembly is prevented by an annular rib (60) connected to the cylindrical body portion (18), an end cap (66) secured to the compression nut forming a stop for the annular rib in the event of the assembly becoming disengaged.
Again, in U.S. Pat. No. 5,350,200 a tube coupling assembly for connecting first and second fluid-carrying tubes together is disclosed. Disengagement of the assembly is prevented by a plurality of circumferentially spaced and axially extending resilient fingers protruding from a barrel portion of a ferrule, said fingers engaging circumferentially spaced and axially extending grooves within the barrel portion of a coupling nut. Similarly, in U.S. Pat. No. 5,188,398 a redundantly locked fluid coupling is disclosed which utilizes ratcheting teeth or sawtooth teeth in a circumferential surface of a coupling nut to prevent a disengagement of a fluid coupling. In U.S. Pat. No. 5,131,690 a self locking connector is disclosed which prevents disengagement between two fluid carrying tubular members by interposing a collar having longitudinal slots in its forward end between the tubing to be temporarily interconnected.
Additional coupling locking devices are disclosed in U.S. Pat. Nos. 5,127,679; 3,586,351, 1,639,407; and 1,139,671. In U.S. Pat. No. 5,127,679 a bushing with inner teething for locking a joint together is disclosed; U.S. Pat. No. 3,586,751 teaches locking nuts on a combination taper and standard threaded tube; U.S. Pat. No. 1,639,407 describes deformable grooves within a nut and bolt combination to effect a locking union; U.S. Pat. No. 1,139,671 discloses a locking union between two pipe threads in which the threads of one compression nut eventually distort within the threads of a second compression nut, effecting a locking of the joint.
While these various devices disclose useful fluid carrying joint connections they do not address the problem of providing a reliable flare nut union operating over a variety of environmentally induced stressful conditions.
It is therefore a principal object of the invention to provide a reliable, leak-free flare nut union.
A further object of the invention is to provide a leak-free flare nut assembly to replace existing flare nut installations.
An additional object of the invention is to provide a flare nut union with a redundant flare nut securing assembly.
Still another object of the invention is to provide a leak-free flare nut union compatible with existing flare nut installations.
Another object of the invention is to provide a low cost, economical, and easy to install leak-free flare nut union.